Odd buzzing issue...

[pantherairsoft]

Hi guys

I know there is a wealth of info about buzzing issues on here, but this is an odd one...

Played a gig tonight. Set up my rig. No problems. As soon as I connected my bass to it there was a loud electrical buzz... Kind of like being between radio stations...

Changed all leads - same issue
Changed the power socket being used a well as extensions - same issue

I assumed my amp head didn't like crap wiring in the venue... But... Connected out keyboard player to my amp... Nothing... Nice and silent like it should be.

Ok, so I bow assume it's an issue with my bass... Start playing with the pots and find that turning the mid pot all the way up removes 90% of the buzz, rolling the mid pot off make it much much louder. Something to do with earthing in the bass or a dodgy pot. At this point another bassist arrives and we try his bass. No problem. That solves it. The amp is fine and it's the bass.

Later I get back to the studio and set my rig up and plug in to start elimating things to get to the root of the issue... And it's gone. Everything perfect.

I've know amps to buzz and disagree with badly wired venues... But is it actually possible that a bass can disagree with a venue as it's only happened there?

Shep

[Bloodaxe]

Sounds like your shielding wants a bit of looking into, something's getting through.

Did the venue have any house lighting controlled by a dimmer circuit? They're known for playing havoc with instruments.

Which bass & what p/ups?

P.

[icastle]

[quote name='pantherairsoft' post='1051183' date='Dec 8 2010, 12:21 AM']Something to do with earthing in the bass or a dodgy pot. At this point another bassist arrives and we try his bass. No problem. That solves it. The amp is fine and it's the bass.[/quote]

Yep.
You've pretty much eliminated the amp and cables from the scenario.
Your bass has either got a bad earth joint or shielding that isn't up to scratch.
You're going to have to go digging around inside and look for bad or suspect looking joints as a first step and if that doesn't provide an answer you're going to have to look at the shielding.

[pantherairsoft]

[quote name='Bloodaxe' post='1051199' date='Dec 8 2010, 12:52 AM']Sounds like your shielding wants a bit of looking into, something's getting through.

Did the venue have any house lighting controlled by a dimmer circuit? They're known for playing havoc with instruments.

Which bass & what p/ups?

P.[/quote]

There were some lights but just on or off, no dimmer.

My RIM Marseer. Delano HS pups, Aguilar pre


[quote name='icastle' post='1051205' date='Dec 8 2010, 01:02 AM']Yep.
You've pretty much eliminated the amp and cables from the scenario.
Your bass has either got a bad earth joint or shielding that isn't up to scratch.
You're going to have to go digging around inside and look for bad or suspect looking joints as a first step and if that doesn't provide an answer you're going to have to look at the shielding.[/quote]

But only having that issue in that venue....? The bass performs fine in the studio, home and 2 other venues so far...

[bobbass4k]

If the mid pot eliminated it the I'd say it's a certain frequency of interference, there's a billion things it could be, somebody else's amp, a PA speaker, even something as anal as the wattage of lightbulb they were using. If it happens again go through possible noise sources one by one (anything electrical is a possible noise source), try playing elsewhere in the room, turn off every bit of electrical equipment one by one etc. You could just reshield (or indeed shield) the control cavity, but I know I'd want to find out what was doing it.

Edited December 8, 2010 by bobbass4k

[icastle]

[quote name='pantherairsoft' post='1051206' date='Dec 8 2010, 01:06 AM']There were some lights but just on or off, no dimmer.

My RIM Marseer. Delano HS pups, Aguilar pre




But only having that issue in that venue....? The bass performs fine in the studio, home and 2 other venues so far...[/quote]

There's loads of stuff that could have been responsible for it - even something as daft as a beer pump living on the same ring main could do it (does this in my local in fact!).
If your bass is not particularly well shielded it can act as a big aerial for any electronic noise that's floating around.

[pantherairsoft]

Agreed.

I was the first to set up and I discovered it.

No PA on, no other amps. Tried a fee power sockets and 3 different locations around the room for placing the amp (as I assumed it was an amp issue to start with). Even turned the lights off!

No change there at all.

I'll have a good look at the wiring around the mid pot tomorrow. Shielding has just been done as it's a new bass and from what I can see on inspection is a very very professional job within the control cavity... Which is why the issue surprised me.

Pic taken before the pups were in so this isn't as it wired at the mo... But shows the shielding job...


The cavity cover is coated in the same way.

Edited December 8, 2010 by pantherairsoft

[pantherairsoft]

[quote name='bobbass4k' post='1051213' date='Dec 8 2010, 01:19 AM']If the mid pot eliminated it the I'd say it's a certain frequency of interference[/quote]

Agreed.

Thing that was odd though was that altering the EQ on the amp made no difference, but changing the inboard bass pre did.

The bass pre has a 400/800 hz switch... It both positions, boosting the mods reduced the noise (but never elimated it). My amp head can select frequency as well... But boosting or cutting the same frequencies made no difference from the amp...

[Mr. Foxen]

Do some continuity testing on that shielding, looks nice, but some has conductive glue and some doesn't, I don't see and solder joints if it happens to be stuff that doesn't.

Also, CRT monitors/TVs are a source of lots of noise if you want to find is noise is making it through, so waving your bass around in front of a screen should reveal if it is picking up noise from a source like that.

[pantherairsoft]

Cheers for the advice everyone.

I've been totally unable to recreate the issue outage of the venue. Have been playing around with my rig and bass this morning... Tried loads of of the electronics on the same mains ring, PA, wireless mic receiver etc... Had my bass right up against a TV and a PC monitor to see if it created interference... Nothing. I can't find any evidence that there's an issue with the bass at all...

Maybe I have to accept that bass & that venue don't like each other!

[MarkBassChat]

On the photos above I don't see a point where the preamp ground is connected to the copper shielding. I assume it is somewhere connected, isn't it?

Mark

[pantherairsoft]

There is a large amount of wiring missing from there… Pic was taken before pickups were installed… The Aguliar pre is earthed to the jack (as per the wiring instructions with the pre) and not to the copper shielding (which is for outside interference).

Updated pics as it stands today




And may I add that Robbie has done a wicked tidy job of wiring that pre up with those pups in what is really quite a small control cavity!

Edited December 8, 2010 by pantherairsoft

[icastle]

[quote name='pantherairsoft' post='1051603' date='Dec 8 2010, 01:00 PM']There is a large amount of wiring missing from there… Pic was taken before pickups were installed… The Aguliar pre is earthed to the jack (as per the wiring instructions with the pre) and not to the copper shielding (which is for outside interference).

Updated pics as it stands today




And may I add that Robbie has done a wicked tidy job of wiring that pre up with those pups in what is really quite a small control cavity![/quote]

Very tidy looking job.
None of the pots are earthed though?

[pantherairsoft]

[quote name='icastle' post='1051693' date='Dec 8 2010, 02:05 PM']Very tidy looking job.
None of the pots are earthed though?[/quote]

No… Just the pre-amp as per wiring diagrams…

Before you say it… Yes, I think I am realising why the bass did not like the venue...

[pantherairsoft]

Not so tidy shot of the inside of my Roscoe…



That blob of solder in the middle of the shot has wire coming from it to each pot… I assume a similar set up on the RIM would be a good idea?

[icastle]

[quote name='pantherairsoft' post='1051713' date='Dec 8 2010, 02:21 PM']Not so tidy shot of the inside of my Roscoe…
That blob of solder in the middle of the shot has wire coming from it to each pot… I assume a similar set up on the RIM would be a good idea?[/quote]

Yep - I certainly would.
The rule of thumb is that you can't technically 'over earth' guitar electronics.

[wesfinn]

if it was only in the venue then i would say it was almost certainly interference. Robbie has shielded the cavity more than well enough. But as everyone is saying it could be anything in the venue from fruit machines to beer pumps to light fittings!

If you are worried about it though i'd take it to Robbie and get him to install an earth eylet on the base of the cavity and then earth from the top of each pot to the eyelet.

[BanditSid]

Does your amp have active and passive inputs ? If so,which do you use ?

The passive input tends to be very high impedance, which then makes the guitar more susceptible to interference pickup. Try the active input which is usually around 10k, the gain may be slightly lower but it might help with interference pickup.

[pantherairsoft]

[quote name='wesfinn' post='1052152' date='Dec 8 2010, 09:40 PM']if it was only in the venue then i would say it was almost certainly interference. Robbie has shielded the cavity more than well enough. But as everyone is saying it could be anything in the venue from fruit machines to beer pumps to light fittings!

If you are worried about it though i'd take it to Robbie and get him to install an earth eylet on the base of the cavity and then earth from the top of each pot to the eyelet.[/quote]

Already on it! Spoke to Robbie yesterday who suggested we do the exact same thing... We are hooking up in Jan anyway and he's planning to do this at that point.

[quote name='BanditSid' post='1052189' date='Dec 8 2010, 10:17 PM']Does your amp have active and passive inputs ? If so,which do you use ?

The passive input tends to be very high impedance, which then makes the guitar more susceptible to interference pickup. Try the active input which is usually around 10k, the gain may be slightly lower but it might help with interference pickup.[/quote]

Just the one input on both the amp heads I own (EBS HD350 & EBS Fafner). It was the HD350 I was using that night, but being another bass was fine, as well as a keyboard through the amp I'm pretty confident it's the bass earthing that was the issue.